1. Field of the Invention
The present invention relates to a magnetic head transferring device of a hard disk drive and, more particularly, to a magnetic head transferring device of a hard disk drive having an improved structure for unlocking a magnetic head locked in a parking area.
2. Description of the Related Art
As shown in FIG. 1, a hard disk drive is composed of a hard disk 20 rotatably installed on a base 10 for recording and reproducing information and a magnetic head transferring device for moving a magnetic head 50 to a desired track position on the hard disk 20 to record and read information. Here, the surface of the hard disk 20 is divided into a recording area 22 in which information is recorded and a parking area 21 provided at the inner portion of the hard disk 20 where the magnetic head 50 is placed when the rotation of the hard disk 20 stops.
The magnetic head transferring device has a rotor 30 installed to be capable of pivoting around a pivot shaft 34 provided on the base 10 and on which the magnetic head 50 is mounted, a stator 40 for actuating the rotor 30 to pivot by an electromagnetic force, and a locking means for locking the rotor 30 after the magnetic head 50 is placed in the parking area 21. The rotor 30 is composed of a suspension portion 31 for supporting the magnetic head 50, a swing arm 32 installed to be capable of pivoting around the pivot shaft 34 via pivot bearings 34a, and a bobbin 33 around which a coil 35 for generating an electromagnetic force is wound. The stator 40 has a magnet 41 and a yoke 42 for forming a magnetic field. Thus, as an electromagnetic force is generated due to interaction between the magnetic field generated by the magnet 41, the yoke 42, and the current flowing in the coil 35, the rotor 30 is caused to pivot in a direction according to Fleming's left-hand rule.
The locking means is composed of a damper 60 coupled to a protrusion 36 provided at an end of the bobbin 33 of the rotor 30, a first magnetic member 61 which is bonded at an end of the damper 60, and a second magnetic member 43 installed on the stator 40. When the magnetic head 50 installed at the suspension portion 31 enters the parking area 21 of the hard disk 20 as the rotor 30 is pivoted, the first and second magnetic members 61 and 43 are attracted and stick to each other by a magnetic force, as shown in FIG. 1. Thus, the rotor 30 remains in a locked state in which the first and second magnetic members 61 and 43 are stuck to each other, unless an electromagnetic force for pivoting the rotor 30 operates again.
Magnets can be used as the first and second magnetic members 61 and 43. A normal metal piece capable of being magnetized by a magnetic force can also be used for at least one of the first and second magnetic members 61 and 43. The first and second magnetic members 61 and 43 can be magnetized by a magnetic field formed by the magnet 41 and the yoke 42.
To prevent the rotor 30 from being unlocked when a strong external impact is applied, an increase in the magnetic force is required for attracting the first and second magnetic members 61 and 43. However, when a strong magnetic force is used, the unlocking of the rotor 30 is difficult.
Typically, in order to pivot the locked rotor 30 again, an electromagnetic force stronger than that of the coupling force between the first and second magnetic members 61 and 43 is applied to separate them. When the first and second magnetic members 61 and 43 are stuck to each other with a strong magnetic force, a separation force greater than the strong magnetic force, is required. When the first and second magnetic members 61 and 43 are separated by a strong separation force, the rotor 30 abruptly rotates such that the magnetic head quickly travels toward the outside edge of the hard disk, as if the rotor had received an external impact. The strong electromagnetic force continues to act on the rotor during at least part of the rotor's rotation, causing excessive rotation of the rotor. Thus, because the magnetic head 50 is moved too far out of the recording area 22 of the disk 20, extra time is required to return the magnetic head 50 to the desired position, and moreover, the magnetic head 50 may be damaged by bumping against other elements.
Therefore, a smooth unlocking of the magnetic head, in spite of the increased coupling force between the first and second magnetic members 61 and 43, is required.